1. Technical Field
The present invention relates to an illumination switch device, which illuminates an illumination portion formed in a manipulation surface of a manipulation knob by using light of a light source.
2. Related Art
In an in-car switch device, which is used to perform an on-off switching operation by an operation of pushing a manipulation knob, an illumination mechanism is provided, which is capable of illuminating an illumination portion formed in a manipulation surface of the manipulation knob by using light of an embedded light source in order to ensure the visualizing ability in a dark place such as a tunnel or at night. As an example of the illumination switch device, there is known an illumination switch device having a structure shown in FIG. 2 (for example, see Japanese Patent No. 4080322).
As shown in FIG. 2, the known illumination switch device includes a manipulation knob 11, which has an illumination portion 10 formed in the upper surface thereof, a hollow slider 12, which is incorporated into the manipulation knob 11, a casing 13, which elevatably guides the slider 12, a print circuit board 14, which is disposed inside the casing 13, a push switch (switch element) 15, which is mounted on the print circuit board 14, an LED (Light Emitting Diode) 16, which serves as a light source and is mounted on the print circuit board 14, where the LED 16 is disposed right below a hollow portion of the slider 12. The manipulation knob 11 includes a body 17, which is formed of a light transmitting resin and a light shielding coating material 18, which is coated on the outer surface thereof. The illumination portion 10 is formed by removing a part of the light shielding coating material 18 from the upper surface of the body 17 so as to have a desired shape. The peripheral edge portions of the manipulation knob 11 are respectively formed as skirt portions 11a protruding downward, and both facing side walls of the skirt portions 11a are respectively provided with locking holes 11b. In addition, each locking hole 11b is formed through each skirt portion 11a. The slider 12 is formed of a light shielding resin, and the upper outer surface thereof is provided with a pair of locking claws 12a. Then, when the manipulation knob 11 is disposed so as to cover the upper portion of the slider 12 and the locking holes 11b are respectively inserted and snap-connected to the corresponding locking claws 12a, the manipulation knob 11 is incorporated into the slider 12. In addition, the slider 12 can elevate via a guide hole 13a as a sliding surface of the casing 13, and the upper portion of the slider 12 including the snap-connected portion of the manipulation knob 11 protrudes upward from the guide hole 13a. Further, a stem 15a of a push switch 15 comes into contact with the lower end portion of the slider 12, and the slider 12 is urged upward by an elastic repellent force of a returning spring (not shown) provided inside the push switch 15.
In the illumination switch device with such a configuration, when the body 17 of the manipulation knob 11 is formed of, for example, a creamy white light transmitting resin, and the black light shielding coating material 18 is coated on the outer surface thereof except for the illumination portion 10, it is possible to see the illumination portion 10, which is seen as creamy white over black in a bright place. On the other hand, when the LED 16 is turned on in a dark place or at night, light of the LED 16 is irradiated to the rear surface of the manipulation knob 11 via the inner space of the slider 12 so as to reach the illumination portion 10 via the body 17 as shown by the arrow A in FIG. 2. Accordingly, it is possible to see the illumination portion 10 illuminated as creamy white in a dark place.
However, in the known illumination switch device, each locking hole 11b snap-connected to each locking claw 12a of the slider 12 is formed in the skirt portion 11a of the manipulation knob 11. For this reason, a problem arises in that the light of the LED 16 reaches the locking hole 11b via the inside of the body 17 during the illumination operation and the light leaks from a ceiling surface of the locking hole 11b to the outside of the manipulation knob 11 as shown by the arrow B in FIG. 2.
In addition, a structure shown in FIG. 3 can be considered as solving means for preventing the optical leakage. In detail, the rear surface of the manipulation knob 11 is provided with a pair of connection pieces 11c, which protrudes backward, and the locking holes 11b provided in the connection pieces 11c are respectively snap-connected to the locking claws 12a formed in the outer surface of the slider 12. In this case, if the locking hole 11b is formed in the connection piece 11c at a position completely covered by the skirt portion 11a of the manipulation knob 11, that is, a position above the lower end portion of the skirt portion 11a, it is possible to shield the light leaking from the locking hole 11b to the outside of the manipulation knob 11 by using the skirt portion 11a. However, the locking claw 12a is required to be formed at a position below the lower end portion of the skirt portion 11a due to a limitation in a structure of a mold, and the locking hole 11b is located above the casing 13 so as to be exposed to the outside. For this reason, it is not possible to sufficiently prevent the light from leaking from the locking hole 11b. In addition, the slider 12 incorporated into the manipulation knob 11 is elevated by being guided via the guide hole 13a of the casing 13. Since the outer surface of the slider 12 is snap-connected to the connection piece 11c of the manipulation knob 11, when the slider 12 moves down via the guide hole 13a, the slider 12 cannot move down any more at the time point when the lower end portion of the connection piece 11c collides with the upper surface of the casing 13. As a result, the slider 12 is largely limited by the connection piece 11c having a long guide length, and for example, the push switch 15 having an extremely short stroke length is required to be used, thereby causing a problem in that a degree of freedom in design deteriorates.